Just completed a fan delete mod on a '96 328is. Replaced the thermostat, aux fan switch, fan pulley, thermostat housing and belts. Flushed the coooling system and re-filled with distilled water, BMW blue coolant and a bottle of Redline water wetter. Ran the car three times and added more water each time as level went down. First time, I noticed a leak between the lower radiator hose and the thermostat housing - I forgot to completely tighten the hose clamp. Other than that, no leaks. Last two times I drove it, I noticed that the temp gauge would stay right in the middle and then suddenly start moving quickly towards the red zone. I turned around and went straight home the first time but by then the temperature had gone back to normal. The second time, it got all the way up to the red zone just before I pulled into the driveway. I jumped out and opened the hood just as the auxiliary fan came on. The temperature went right down and stayed down as the fan went on and off several times. Then, it just stopped going on and I had to shut the car down because the temperature went right up into the red zone. I checked both fuses for the fan and they were both fine. Any ideas?

Just needed more patience. The cooling system still had air in it. Once the car cooled, the expansion tank was completely empty. Refilled it, ran the car again, let it cool, filled the expansion tank again as it was half empty and now the temp gauge sits rock solid on the middle and the fan kicks in just like it should. Lesson learned: Refilling the cooling systems on these cars takes patience. Make sure have your A/C controls set to full heat so that your heater core is emptied when you drain and is filled when you add the new coolant/water/wetting agent mix or else you will never get all of the air out.

Patience is really the key here. If the didn't work as of the moment, try changing it to a new or, or better yet, try to monitor all the parts of your car if somethings really bothering it at all. Or ask for some good old advice to the mechanic on this situation.